The invention is based on a fuel injection nozzle for internal combustion engines as generically defined hereinafter. In an injection nozzle of this type, known from German Offenlegungsschrift DE-OS 40 06 488, the valve needle has a plurality of axially parallel longitudinal grooves in the circumference of the piston embodied as a collar, which extend downstream from the face end of the piston that defines the pressure chamber to the valve cone of the piston. When the valve needle opens, the region of the longitudinal grooves near the valve cone is uncovered progressively as an injection cross section; the resultant flow vector is always defined by the shortest path from the inlet of the longitudinal groove to the injection cross section. Since the longitudinal grooves extend axially parallel as far as the injection cross section, a strongly axial directional component is imparted to the injection stream; orientation at a predetermined cone angle adapted to the engine combustion chamber is not possible.
A precise alignment of the injection streams at a predetermined cone angle is present in a fuel injection nozzle according to European Patent Disclosure EP-A-209 244, in which the injection direction is determined by injection ports that pierce the shaft of the hollow-drilled valve needle at an obtuse cone angle near the valve cone. Flaring open or breathing of the hollow valve needle at high pressures can cause problems with respect to reliable function in this embodiment of the valve needle. Moreover, the axial bore in the shaft of the valve needle is a hindrance to miniaturizing the injection nozzle.